Photoelectric-conversion apparatus and image-pickup system

ABSTRACT

A photoelectric-conversion apparatus includes a photoelectric-conversion area where a plurality of photoelectric-conversion elements configured to convert incident light into electrical charges, a plurality of floating-diffusion areas, a plurality of transfer-MOS transistors configured to transfer electrical charges of the photoelectric-conversion element to the floating-diffusion area, and a plurality of amplification-MOS transistors configured to read and transmit a signal generated based on the transferred electrical charges to an output line are provided. An antireflection film is provided on a light-receiving surface of the photoelectric-conversion element. The gate of the amplification-MOS transistor is electrically connected to one floating-diffusion area by providing one conductor in a single contact hole, and the anti-reflection film covers the photoelectric-conversion area except a base part of the contact hole.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a photoelectric-conversion apparatusand particularly relates to a metal oxide semiconductor (MOS)photoelectric-conversion apparatus.

2. Description of the Related Art

Photoelectric-conversion apparatuses have been rapidly growing indemand, as image-pickup devices of two-dimensional-image-input devices,notably digital-still cameras and video camcorders and/orone-dimensional-image readers, notably facsimiles and scanners. In theabove-described photoelectric-conversion apparatuses,MOS-photoelectric-conversion apparatuses using a MOS transistor areused, so as to read a signal. In the MOS-photoelectric-conversionapparatus, both a photoelectric-conversion area and a peripheral-circuitarea can be formed at the same time by performing complementary metaloxide semiconductor (CMOS)-manufacturing processing. Therefore, theMOS-photoelectric-conversion apparatus can be formed by performing amanufacturing processing that is easier than that performed formanufacturing a charge-coupled device (CCD).

When performing the CMOS-manufacturing processing, a contact configuredto electrically connect a semiconductor area provided on a semiconductorsubstrate and/or a gate electrode of a transistor to upper wiring isused.

A shared contact is used for connecting the semiconductor area to thegate electrode by using a single conductor without concern for thetwo-dimensional distance between the semiconductor area and the gateelectrode that are connected to the contact and/or the two-dimensionaldistance between contacts. The above-described technology is often usedfor a static random access memory (SRAM), since the technology isadvantageous to form a smaller semiconductor device by doing layout.

Japanese Patent Laid-Open No. 2002-368203 discloses an example where theabove-described shared contact is used for forming aCCD-photoelectric-conversion apparatus. According to Japanese PatentLaid-Open No. 2002-368203, the shared contact is included in anoutput-buffer circuit having a MOS transistor in which a gate-electrodeunit is electrically connected to a floating-diffusion area, as a drivetransistor. Subsequently, an electrical-charge-conversion coefficient isincreased due to a reduced capacity.

According to Japanese Patent Laid-Open No. 2002-368203, the sharedcontact is provided in an output unit of a horizontal CCD, and providedin an area different from a photoelectric-conversion area where aphotoelectric-conversion element such as a photodiode is formed. On theother hand, through investigations performed by inventors of the presentinvention, a new problem is found, the new problem being caused byproviding the shared contact in the photoelectric-conversion area wherethe photoelectric-conversion element is provided.

The area of a contact hole used to form the shared contact should belarger than that of a contact hole used to form an ordinary contact. Inthat case, the etching rate of the contact hole used to form the sharedcontact becomes higher than that of the contact hole used to form theordinary contact due to the microloading effect. Subsequently, theoveretching amount of a contact-hole unit used to form the sharedcontact becomes larger than in the case where the ordinary contact holeis formed. When the overetching amount is increased in thephotoelectric-conversion area where the photoelectric-conversion elementis provided, an increased number of noises to thephotoelectric-conversion element are produced and the image qualitydeteriorates.

Accordingly, the present invention has been achieved, so as to use ashared contact in a photoelectric-conversion area without increasing anoise to a photoelectric-conversion element.

SUMMARY OF THE INVENTION

For solving the above-described problems, a photoelectric-conversionapparatus according to an embodiment of the present invention includes aphotoelectric-conversion area having a plurality ofphotoelectric-conversion elements configured to convert incident lightinto electrical charges, a plurality of floating-diffusion areas, aplurality of transfer-MOS transistors configured to transfer electricalcharges of the photoelectric-conversion element to thefloating-diffusion area, a plurality of amplification-MOS transistorsconfigured to read and transmit a signal generated based on thetransferred electrical charges to an output line, and an antireflectionfilm provided on a light-receiving surface of thephotoelectric-conversion element and a plurality of wiring layers. Onegate of the amplification-MOS transistor is electrically connected toone floating-diffusion area by one conductor provided in a singlecontact hole, where the electrical connection is not via the pluralityof wiring layers, and the antireflection film is provided, so as tocover at least a part of each of an upper part of the floating-diffusionarea and an upper part of the gate of the amplification-MOS transistorexcept the base part of the contact hole.

Other features and advantages of the present invention will be apparentfrom the following description taken in conjunction with theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example schematic plan view of a photoelectric-conversionapparatus according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view showing the configuration of aphotoelectric-conversion apparatus according to a first embodiment ofthe present invention.

FIG. 3 is a schematic plan view showing the configuration of thephotoelectric-conversion apparatus according to the first embodiment.

FIG. 4 is a schematic plan view showing the configuration of aphotoelectric-conversion apparatus according to a second embodiment ofthe present invention.

FIG. 5 is an equivalent-circuit diagram showing the configuration of thephotoelectric-conversion apparatus according to the second embodiment.

FIG. 6 is a block diagram illustrating an image-pickup system.

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention.

DESCRIPTION OF THE EMBODIMENTS

The configurations of embodiments of the present invention will bedescribed. According to an embodiment of the present invention, aphotoelectric-conversion area is an area where a plurality ofphotoelectric-conversion elements and metal-oxide-semiconductor (MOS)transistors configured to read a signal generated based on an electricalcharge of the photoelectric-conversion element are provided. A pluralityof the MOS transistors may be provided for each of thephotoelectric-conversion elements so that the electrical charge can beamplified.

A peripheral-circuit area is an area where a circuit configured to drivethe MOS transistors provided on the above-describedphotoelectric-conversion area, a circuit configured to amplify a signaltransmitted from the photoelectric-conversion area, and so forth areprovided.

FIG. 1 shows a plan view of a photoelectric-conversion apparatus. Aphotoelectric-conversion area 111 is provided. If the unit of a signalread from a single photoelectric-conversion element is determined to bea pixel, an area where electric-conversion elements are provided may bereferred to as a pixel area. The pixel is the minimum unit of a singlephotoelectric-conversion element and an element assembly provided toread a signal from the photoelectric-conversion element and transmit theread signal to an output line. The element assembly includes a singlephotoelectric-conversion element and a single transfer-MOS transistor.Further, a single floating-diffusion area, a single amplification unitincluding an amplification-MOS transistor or the like, and a singlereset unit including a reset-MOS transistor or the like are provided ineach of the element assemblies. The elements included in the elementassembly can be shared between at least two photoelectric-conversionelements adjacent to each other. In that case, the pixel is also definedas the minimum unit of the element assembly configured to read a signalof a single photoelectric-conversion element.

A signal-processing circuit 112 is provided to amplify the signal readfrom the photoelectric-conversion area 111. However, thesignal-processing circuit may be provided, as not only an amplificationcircuit but also a circuit configured to remove a noise of a pixel byperforming correlated-double-sampling (CDS) processing. Further, thesignal-processing circuit may simply be a circuit configured to convertsignals read from a plurality of columns in parallel into serialsignals.

A vertical-shift register 113 is configured to drive the MOS transistorprovided in the photoelectric-conversion area 111. A horizontal-shiftregister 114 is configured to drive the MOS transistor of thesignal-processing circuit 112. The signal-processing circuit 112, thevertical-shift register 113, and the horizontal-shift register 114 maybe included in the peripheral-circuit area. Further, whenanalog-to-digital (AD) conversion is performed in thephotoelectric-conversion apparatus, an AD-conversion circuit may beincluded in the peripheral-circuit area.

According to an embodiment of the present invention, a gate electrode ofthe amplification-MOS transistor provided in thephotoelectric-conversion area is connected to the floating-diffusionarea by embedding a conductor in a single contact hole, where theelectrical connection is not via the plurality of wiring layer. Then, anantireflection film is provided on the light-receiving surface of thephotoelectric-conversion element, so as to cover thephotoelectric-conversion area 111 except the base part of theabove-described contact hole.

Hereinafter, embodiments of the present invention will be described indetail with reference to the attached drawings.

First Embodiment

FIG. 2 shows a schematic sectional view of configurations of aphotoelectric-conversion area and a peripheral-circuit area of aphotoelectric-conversion device. FIG. 3 shows a plan view of thephotoelectric-conversion area. As shown in FIG. 2, aphotoelectric-conversion area 101 and a peripheral-circuit area 102 areprovided. FIG. 2 is a sectional view of the photoelectric-conversionarea 101 cut along lines A-A′ and B-B′.

A semiconductor area 103 of the first conductive type and a part of asemiconductor area 104 of the second conductive type generate aphotodiode functioning as a photoelectric-conversion element. Thefirst-conductive-type semiconductor area 103 is of the same conductivetype of that of a signal charge. When the signal charge is an electron,the first-conductive type semiconductor area 103 becomes an N-typesemiconductor area. A semiconductor area 105 of the second conductivetype is provided to reduce a dark current. Further, an opticalantireflection film 106 is provided on the light-receiving surface ofthe photodiode, so as to reduce interface reflection which occurs on thesurface of the photodiode. The antireflection film 106 may have alaminate including silicon nitride (SiN) and silicon monoxide (SiO). Theantireflection film 106 covers the photoelectric-conversion area 101except the base part of a contact hole which will be described later.Here, it is preferable that the antireflection film 106 cover the entirephotoelectric-conversion area 101. However, the antireflection film 106should cover at least the light-receiving surface of thephotoelectric-conversion element, the top face of an electrode where ashared contact is formed, and a part of the top face of thesemiconductor area where the shared contact is formed.

Specifically, the gate of the amplification-MOS transistor and thefloating-diffusion area are electrically connected to each other by theshared contact. By arranging the antireflection film 106 in theabove-described manner, it becomes possible to reduce damage to asemiconductor substrate, the damage being caused by overetchingperformed at the time where a contact hole used to form the sharedcontact is formed. Further, it is preferable that the antireflectionfilm 106 be provided, so as not to cover the base part of a contactother than the shared contact provided in the photoelectric-conversionarea 101. The contact other than the shared contact includes a contactprovided to connect the gate of each of the MOS transistors to wiring.The contact other than the shared contact further includes a contactprovided to connect the drain of each of the reset-MOS transistor andthe amplification-MOS transistor to power wiring. Still further, thecontact other than the shared contact includes a contact connecting thesource of the amplification-MOS transistor to signal wiring.

Further, the antireflection film 106 may be provided, so as not to coverat least a single part of an element-isolation area provided on thephotoelectric-conversion area 101. Further, since the MOS transistorsprovided on the peripheral-circuit area have a lightly-doped-drain (LDD)structure, it is preferable that the antireflection film 106 beprovided, so as not to cover the peripheral-circuit area.

A gate 107 of the transfer-MOS transistor is provided to transfer anelectrical charge of the semiconductor area 103. A semiconductor area108 is of the first conductive type and an area to which thetransfer-MOS transistor transfers an electrical charge. Since a voltagechanging based on the transferred electrical charge is read, asdescribed later, the first-conductive-semiconductor area 108 can bereferred to as an electrical charge-to-voltage conversion unit. Further,when an electrical charge is transferred by the transfer-MOS transistor,the first conductive type-semiconductor area 108 is in anelectrically-floating state. Therefore, thefirst-conductive-semiconductor area 108 may be referred to as afloating-diffusion (hereinafter referred to as FD) area. A voltagesignal is read and transmitted to a signal line by the amplification-MOStransistor provided on the photoelectric-conversion area 101. Afterthat, a read circuit including a MOS transistor 110 provided on theperipheral-circuit area 102 reads the voltage signal outside thephotoelectric-conversion apparatus.

According to the first embodiment, an electrical connection between theFD area 108 and a gate 117 of the amplification-MOS transistor isachieved by a conductor (shared contact) 119 provided in one and thesame contact hole. The shared contact may be referred to as aninterconnect.

Next, a schematic plan view of FIG. 3 will be described. Aphotoelectric-conversion element 201, a gate 202 of the transfer-MOStransistor, an FD area 203, which is the drain of the transfer-MOStransistor, and a gate 205 of the amplification-MOS transistor areprovided. The gate 205 includes not only a part provided on the channelof the MOS transistor but also a wiring part provided on theelement-isolation area.

The electrical connection between the FD 203 and the gate 205 of theamplification-MOS transistor is achieved by a shared contact 204. Thegate 205 of the amplification-MOS transistor actually comes in contactwith the shared contact at a part provided on the element-isolationarea.

The shared contact may include tungsten, amorphous silicon, polysilicon,and so forth. Further, when metal is used to form the shared contact,the metal and a barrier-metal material including titanium, titaniumnitride, tantalum, and so forth may be stacked onto each other. Thebarrier-metal material is used to prevent metallic elements from beingdiffused due to heat treatment. When the electrical connection betweenthe FD AREA 108 and the gate 117 of the amplification-MOS transistor isachieved by using the shared contact, the wiring space required toperform wiring connection can be reduced. Further, when theamplification-MOS transistor is shared between adjacentphotoelectric-conversion elements, as described later, different wiringused to connect the adjacent photoelectric-conversion elements and theamplification-MOS transistor to one another is required, which reducesthe aperture ratio. On the other hand, the use of the shared contactallows the amplification-MOS transistor to be shared between theadjacent photoelectric-conversion elements without decreasing theaperture ratio. Further, the number of contact holes can be reduced.

However, when the shared contact is used, it is preferable that the areaof the contact hole be increased. In that case, the etching rate of thecontact hole used to form the shared contact becomes larger than that ofan ordinary contact hole due to a microloading effect. Therefore, it ishighly possible that the overetching amount of the contact hole used toform the shared contact becomes larger than that of the ordinary contacthole. When the overetching amount is increased while the contact hole isformed, the increase causes the element characteristic to deteriorate.Particularly, noise occurs in the photoelectric-conversion element dueto a defect occurring on the semiconductor substrate. Therefore, theoveretching exerts a bad influence on a part near thephotoelectric-conversion element. It is difficult to connect the FD AREA108 to the gate 117 of the amplification-MOS transistor at a partsignificantly distant from the photoelectric-conversion element due tothe above-described configuration. Therefore, when the overetching isperformed, it is difficult to reduce an influence exerted upon thephotoelectric-conversion element.

On the other hand, when an antireflection film reducing the interfacereflection of light incident upon a light-receiving surface is provided,so as to cover a photoelectric-conversion area, as in the firstembodiment, the antireflection film reduces the influence of theoveretching. Subsequently, it becomes possible to achieve smallerelements that construct the photoelectric-conversion apparatus by usingthe shared contact while reducing the overetching influence.

Further, the MOS transistor 110 provided on the peripheral-circuit areamay have the LDD structure, as shown in FIG. 2. At that time, part ofthe MOS transistors provided on the photoelectric-conversion area mayalso have the LDD structure. However, according to the first embodiment,the configurations of the MOS transistors provided on thephotoelectric-conversion area are different from those of the MOStransistors provided on the peripheral-circuit area.

For example, a semiconductor area 111 of the first conductive type witha high impurity density, the first conductive-semiconductor area 111being provided for the drain of the MOS transistor provided on theperipheral-circuit area, is not formed on the FD AREA 108 and thesource-and-drain area of the amplification-MOS transistor 109. A drainis formed by using a semiconductor area 114 of the first conductive typewith a low impurity density. However, in an area electrically connectedto a wiring layer, a semiconductor area 116 of the first conductive typewith a high impurity density is formed under a contact hole 115 and/or ashared contact 119, so as to obtain an appropriate electricalconnection.

Here, the MOS transistor provided on the peripheral-circuit area has theLDD structure, as described above, and a side spacer 113 is provided atthe gate of the MOS transistor. The side spacer 113 may be formed byusing one and the same layer as that of the antireflection film 106 inthe following manner. Namely, the antireflection film 106 is formed sothat the antireflection film 106 covers the photoelectric-conversionarea and the peripheral-circuit area, the photoelectric-conversion areais protected by using a mask, and the entire peripheral-circuit area isetched so that the side spacer 113 is formed.

Semiconductor areas 114 may be formed so that the semiconductor areas114 are self-aligned with gate electrodes 107, 112, and 117. Further,the semiconductor area 114 is also formed under the side spacer 113 ofthe peripheral-circuit area, and the first conductive-semiconductorareas 111 may be formed so that the first conductive-semiconductor areas111 are self-aligned with the side spacers 113. According to theconfiguration shown in FIG. 2, the first conductive-semiconductor area111 is not formed on an area covered by the side spacer 113 and theantireflection film 106. Namely, the antireflection film 106 functions,as a mask used to perform ion injection. The first conductive-typesemiconductor area 111 with the high impurity density is not formed onthe source, the drain, and the FD of the MOS transistor provided on thephotoelectric-conversion area, but only the first conductive-typesemiconductor area 114 with the low impurity density is formed thereon.

When the antireflection film 106 is not etched on thephotoelectric-conversion area, as described above, a damage caused bythe etching to the photoelectric-conversion element can be reduced.Further, after the antireflection film 106 is formed, no processingprocedure is performed, so as to expose the semiconductor surface.Namely, there is no way to expose the semiconductor surface except bythe use of contact holes. Therefore, contaminations caused by metallicelements or the like can be reduced. Subsequently, the occurrence rateof point defects, the point defects occurring at the dark time, can bereduced.

Further, when the MOS transistor provided on the peripheral-circuit areahas the LDD structure and the drain of the MOS transistor provided onthe photoelectric-conversion area is formed, as a semiconductor areawith the same impurity density as that of the LDD area of theperipheral-circuit area, as described in the above-described embodiment,the following effects can be achieved.

In general, in a MOS transistor having the LDD structure, electric-fieldrelaxation can be achieved in an electric-field-relaxation layer with alow density such as the first conductive-type semiconductor area 114described in the above-described embodiment. Theelectric-field-relaxation effect can be increased by reducing thedensity and/or designing a low-density area having a larger width thanbefore. Subsequently, the occurrence of a hot carrier can be reduced andthe reliability and pressure resistance of the MOS transistor can beincreased.

However, when the density of the electric-field-relaxation layer isinappropriately low and the width thereof is inappropriately large, aparasitic resistance or a series resistance of the MOS transistorincreases, which significantly damages the driving power and staticcharacteristic of the MOS transistor. Therefore, in theperipheral-circuit area where the drive power and/or the circuitproperty is important, the width of the electric-field-relaxation layershould be relatively small. On the other hand, in thephotoelectric-conversion area where the electric field should be relaxedso that smaller elements that construct the photoelectric-conversionapparatus are obtained, for example, the electric-field-relaxation areashould be increased in width.

According to the first embodiment, the width of theelectric-field-relaxation layer of the peripheral-circuit area can berelatively small and the electric-field-relaxation area of thephotoelectric-conversion area can be increased. In the MOS transistorprovided in the photoelectric-conversion area of the first embodiment, apart having an actual electric-field-relaxation effect extends from theend of each of the gates 107 and 117 to the first conductive-typesemiconductor area 116 with the high impurity density, the firstconductive-semiconductor area 116 being formed under the contact hole115 and the shared contact 119. The distance from the end of each of thegates 107 and 117 to the area where the impurity density is high can belarger than the MOS transistor provided on the peripheral-circuit area.Subsequently, a large electric-field-relaxation effect can be obtained.Here, the first conductive-semiconductor areas 116 with the highimpurity density can be formed by forming holes including the contactholes 115 and the shared contact 119 and injecting ions through theholes so that the first conductive-semiconductor areas 116 areself-aligned with the contact holes. Subsequently, it becomes possibleto design a transistor in a reduced size. It is preferable that thefirst conductive-type semiconductor areas 116 with the high impuritydensity be formed, so as to obtain an appropriate electrical connection.

Further, when the entire FD area 108 is formed, as anelectric-field-relaxation area with a low density (the firstconductive-type semiconductor area 114 with the low impurity density), apixel defect and a random noise that are caused by the leakage of the FDarea 108 can be decreased. This is because an electric field generatedin each of a PN junction formed between the second conductive-typesemiconductor area 104 and the first conductive-type semiconductor area114, and a junction formed between a channel-stop layer (not shown)formed under the element-isolation area and the first conductive-typesemiconductor area 114 can be relaxed. Further, it is an empirical factthat there is a correlation between the probability of a suddenoccurrence of a large pixel, the sudden large-pixel occurrence beingcaused by a leakage current of the FD area 108, and the electric fieldof the FD area 108. Further, point defects can also be reduced.

Further, the antireflection film 106 may include a silicon-nitride filmincluding hydrogen. In that case, it becomes possible to reduce trapsoccurring on the interface of a transistor and/or the interface of asilicon/silicon-oxide film provided on the surface of thephotoelectric-conversion element effectively.

Further, the MOS transistors provided on the peripheral-circuit area areof the same conductive types as those of the MOS transistors provided onthe photoelectric-conversion area, for example. However, each of the MOStransistors provided on the peripheral-circuit area may have acomplementary-metal-oxide-semiconductor (CMOS) configuration. A MOStransistor of a conductive type opposite to that of each of the MOStransistors provided on the photoelectric-conversion area may have aside-spacer configuration. The above-described effects have asignificant impact on an n-type MOS transistor where hot carriers tendto occur. When each of the MOS transistors provided on thephotoelectric-conversion area and the peripheral-circuit area is then-type MOS transistor, a significantly large effect can be obtained.

However, when each of the MOS transistors provided on thephotoelectric-conversion area is a P-type MOS transistor, thehot-carrier problems becomes less significant. However, it becomes easyto work on a fine pixel.

As described above, in the photoelectric-conversion apparatus accordingto the first embodiment, the FD area and the gate of theamplification-MOS transistor are electrically connected to each otherthrough the shared contact and the photoelectric-conversion area iscovered by the antireflection film provided on the light-receivingsurface of the photoelectric-conversion element. Subsequently, a fineelement can be easily formed and deterioration of the elementcharacteristic can be reduced, the deterioration being caused byoveretching performed when a contact hole used to form the sharedcontact is formed.

It is preferable that each of the MOS transistors have the configurationdescribed in the above-described embodiment. However, without beinglimited to the above-described embodiment, each of the MOS transistorsmay have a different configuration. For example, each of the MOStransistors provided on the photoelectric-conversion area may have thesame configuration as that of each of the MOS transistors provided onthe peripheral-circuit area. Further, the antireflection film may not bethe silicon-nitride film.

Second Embodiment

FIG. 4 is a schematic plan view of a photoelectric-conversion area of aphotoelectric-conversion apparatus according to a second embodiment ofthe present invention. The above-described photoelectric-conversion areais different from the photoelectric-conversion area according to thefirst embodiment in that each of the amplification-MOS transistor andthe reset-MOS transistor is shared among a plurality ofphotoelectric-conversion elements, for example. However, at least atransfer-MOS transistor may be provided for each of thephotoelectric-conversion elements and an amplification transistor may beprovided and shared between at least two photoelectric-conversionelements.

An electrical charge of each of photodiodes 301 and 311 functioning, asthe photoelectric-conversion elements, is transferred to FD areas 303and 313 through gates 302 and 312 of the transfer-MOS transistors. Thetransferred electrical charges are converted into voltage signalsthrough the FD areas 303 and 313. The voltage signals are read by anamplification-MOS transistor 308 forming part of a source-followercircuit, and read and transmitted to the peripheral-circuit area.According to the second embodiment, an electrical connection between theFD areas 303 and 313, and a gate 305 of the amplification-MOS transistor308 is achieved by shared contacts 304 and 314 that area formed by usingone and the same contact hole. FIG. 5 shows the above-describedconfiguration, as an equivalent-circuit diagram. The FD areas 303 and313 are connected to the gate 305 of the amplification-MOS transistor308 by using the shared contacts 304 and 314 formed by embeddingconductors in one and the same contact hole. Further, theamplification-MOS transistor 308 is shared by the plurality ofphotoelectric-conversion elements, whereby the photoelectric-conversionarea can be reduced in size. Further, as shown in FIG. 5, by sharing areset-MOS transistor 404 used to reset photo diodes 401 and 411, and FDareas 403 and 413, the photoelectric-conversion area can further bereduced in size.

Thus, the second embodiment is applied to the two differentphotoelectric-conversion elements. However, the second embodiment canalso be applied to two or more photoelectric-conversion elements.

(Example Image-Pickup System)

FIG. 6 shows an example circuit-block diagram where the above-describedphotoelectric-conversion apparatus is applied to an image-pickup systemincluding a camera or the like. A shutter 1001 is provided in front ofan imaging lens 1002, so as to control an exposure. The light amount iscontrolled by an aperture 1003, as required, and an image is formed in aphotoelectric-conversion apparatus 1004. A signal externally transmittedfrom the photoelectric-conversion apparatus 1004 is processed by animage-pickup-signal-processing circuit 1005. The externally transmittedsignal, which is an analog signal, is converted into a digital signal byan analog-to-digital (A/D) converter 1006. Further, the digital signalis subjected to calculation processing by a signal-processing unit 1007.The processed digital signal is accumulated on a memory 1010 and/ortransmitted to an external device via an external interface (I/F) 1013.The photoelectric-conversion apparatus 1004, theimage-pickup-signal-processing circuit 1005, the A/D converter 1006, andthe signal-processing unit 1007 are controlled by a timing-generationunit 1008. The overall system is controlled by an overallcontrol-and-calculation unit 1009. The externally-transmitted digitalsignal is recorded through a recording-medium-control I/F unit 1011controlled by the overall-control-and-calculation unit 1009, so as torecord an image onto a recording medium 1012.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all modifications, equivalent structures and functions.

This application claims the benefit of Japanese Application No.2006-235933 filed on Aug. 31, 2006, which is hereby incorporated byreference herein in its entirety.

1. A photoelectric-conversion apparatus comprising: aphotoelectric-conversion area having a plurality ofphotoelectric-conversion elements configured to convert incident lightinto electrical charges; a plurality of floating-diffusion areas; aplurality of transfer-MOS transistors configured to transfer electricalcharges of said photoelectric-conversion element to saidfloating-diffusion area; a plurality of amplification-MOS transistorsconfigured to read and transmit a signal generated based on thetransferred electrical charges to an output line; and an antireflectionfilm provided on a light-receiving surface of saidphotoelectric-conversion element and a plurality of wiring layers,wherein one gate of said amplification-MOS transistor is electricallyconnected to one floating-diffusion area by one conductor provided in asingle contact hole, where the electrical connection is not via saidplurality of wiring layers, and wherein said anti-reflection film isprovided, so as to cover at least a part of each of an upper part ofsaid floating-diffusion area and an upper part of the gate of saidamplification-MOS transistor except a base part of said contact hole. 2.The photoelectric-conversion apparatus according to claim 1, furthercomprising a peripheral-circuit area where a second MOS transistor isprovided, said second MOS transistor being configured to perform atleast one of driving of said MOS transistors provided on saidphotoelectric-conversion area and amplification of a signal read fromsaid photoelectric-conversion area, wherein an impurity density of asource and a drain of said MOS transistor provided on saidphotoelectric-conversion area is lower than an impurity density of asource and a drain of said second MOS transistor provided on saidperipheral-circuit area.
 3. The photoelectric-conversion apparatusaccording to claim 1, wherein said antireflection film is provided, soas not to cover the base part of a contact hole provided in saidphotoelectric-conversion area.
 4. The photoelectric-conversion apparatusaccording to claim 1, wherein said antireflection film is provided, soas not to cover at least a part of an element-isolation area provided onsaid photoelectric-conversion area.
 5. The photoelectric-conversionapparatus according to claim 1, wherein said antireflection film isprovided, so as to cover an entire face of said photoelectric-conversionarea except the base part of a contact hole provided in saidphotoelectric-conversion area and at least a part of anelement-isolation area provided on said photoelectric-conversion area.6. The photoelectric-conversion apparatus according to claim 2, whereina side spacer is formed at a gate of said second MOS transistor providedon said peripheral-circuit area and no side spacer is formed for saidMOS transistors provided on said photoelectric-conversion area, andwherein at least a part of said side spacer of said second MOStransistor provided on said peripheral-circuit area is formed by usingthe same film as said antireflection film.
 7. Thephotoelectric-conversion apparatus according to claim 1, wherein saidantireflection film is a silicon-nitride film including hydrogen.
 8. Thephotoelectric-conversion apparatus according to claim 1, comprising: atransfer-MOS transistor for each of said photoelectric-conversionelements; and an amplification transistor shared between at least two ofsaid photoelectric-conversion elements.
 9. An image-pickup systemcomprising: the photoelectric-conversion apparatus according to claim 1;an optical system configured to form an image of light onto saidphotoelectric-conversion apparatus; and a signal-processing circuitconfigured to process a signal externally transmitted from saidphotoelectric-conversion apparatus.